The invention relates generally to the field of cardiopulmonary resuscitation. In particular, the present invention relates to devices and methods for increasing cardiopulmonary circulation during cardiopulmonary resuscitation procedures involving a chest compression phase and a relaxation or decompression phase.
Worldwide, sudden cardiac arrest is a major cause of death and is the result of a variety of circumstances, including heart disease and significant trauma. In the event of a cardiac arrest, several measures have been deemed to be essential in order to improve a patient's chance of survival. These measures must be taken as soon as possible to at least partially restore the patient's respiration and blood circulation. One common technique, developed approximately 30 years ago, is an external chest compression technique generally referred to as cardiopulmonary resuscitation (CPR). CPR techniques have remained largely unchanged over the past two decades. With traditional CPR, pressure is applied to a patient's chest to increase intrathoracic pressure. An increase in intrathoracic pressure induces blood movement from the region of the heart and lungs towards the peripheral arteries. Such pressure partially restores the patient's circulation.
Traditional CPR is performed by active compressing the chest by direct application of an external pressure to the chest. This phase of CPR is typically referred to as the compression phase. After active compression, the chest is allowed to expand by its natural elasticity which causes expansion of the patient's chest wall. This phase is often referred to as the relaxation or decompression phase. Such expansion of the chest allows some blood to enter the cardiac chambers of the heart. The procedure as described, however, is insufficient to ventilate the patient. Consequently, conventional CPR also requires periodic ventilation of the patient. This is commonly accomplished by a mouth-to-mouth technique or by using positive pressure devices, such as a self-inflating bag which delivers air through a mask, an endotracheal tube, or other artificial airway.
In order to increase cardiopulmonary circulation induced by chest compression, a technique referred to as active compression-decompression (ACD) has been developed. According to ACD techniques, the active compression phase of traditional CPR is enhanced by pressing an applicator body against the patient's chest to compress the chest. Such an applicator body is able to distribute an applied force substantially evenly over a portion of the patient's chest. More importantly, however, the applicator body is sealed against the patient's chest so that it may be lifted to actively expand the patient's chest during the relaxation or decompression phase. The resultant negative intrathoracic pressure induces venous blood to flow into the heart and lungs from the peripheral venous vasculature of the patient. Devices and methods for performing ACD to the patient are described in U.S. Pat. Nos. 5,454,779 and 5,645,552, the complete disclosures of which are herein incorporated by reference.
Another successful technique for increasing cardiopulmonary circulation is by impeding air flow into a patient's lungs during the relaxation or decompression phase. By impeding the air flow during the relaxation or decompression phase, the magnitude and duration of negative intrathoracic pressure is increased. In this way, the amount of venous blood flow into the heart and lungs is increased. As a result, cardiopulmonary circulation is increased. Devices and methods for impeding or occluding the patient's airway during the relaxation or decompression phase are described in U.S. Pat. Nos. 5,551,420 and 5,692,498 and co-pending U.S. application Ser. No. 08/950,702, filed Oct. 15, 1997. The complete disclosures of all these references are herein incorporated by reference.
The above techniques have proven to be extremely useful in enhancing traditional CPR procedures. As such, it would be desirable to provide still further techniques to enhance venous blood flow into the heart and lungs of a patient from the peripheral venous vasculature during both conventional and alternative CPR techniques. It would be particularly desirable to provide techniques which would enhance oxygenation and increase the total blood return to the chest during the relaxation or decompression phase of CPR.